Fluorescence optical brighteners

Intrawite . [Crompton Knowles] Fluorescent/optical brighteners for acrylic, nylon, cellulosics, wool, blends. 

Uses Fluorescent optical brightener for nonaq. systems, acrylics, epoxies, other solv.-based coatings, thermoset and thermoplastic resins, plastics, films, and molded goods fabric brightener or whitener for detergent systems for nylon, silk, wool, and acetates (for use with nonionic, anionic, or cationic surfactants)... 

Chem. Descrip. Pyrazoline type Uses Fluorescent optical brightener for aq. inks and coatings Features Relatively good lightfaslness esp. good stability to acids and alkalis rec. for all anionic and nonionic formulations Properties Yel. liq. sp.gr. 1.14 vise. < 100 cps (20 C) pH 3.5-4.5 50-52% solids Use Level 0.1-2.0%... 

The firm of Reckitt Sons in England produced ifecAaftiWue from 1852, a combination of synthetic ullramarine and sodium hydrogen carbonate (sodium bicarbonate). The use of laundry blue was effectively superseded, however, by the introduction of fluorescent optical brighteners. 

Optical brighteners are colourless fluorescent dyestuffs that absorb in the near UV (350-390 nm) and fluoresce in the violet to blue region of the spectrum (425-445 nm). 

Some laundry detergents contain optical brighteners. These are fluorescent dyes that glow blue-white in ultraviolet light. The blue-white color makes yellowed fabrics appear white. 

Lawrence and Ducharme [489] have described a fast, simplified method for the detection of fluorescent whiteners in polymers, in which the polymer dissolution was applied directly to the thin layer. Also the separation of optical brighteners (Leucopur EGM, Azur 4, Azur 5, Hostalux ABC, Uvitex OB, Eastobrite OB) from plastics and migration into water and olive oil was studied by HPTLC on RP-18 silica using various mobile phase mixtures and UV detection [490]. 

A collection of UV spectra of plasticisers, fluorescent whitening agents (optical brighteners), UV absorbers, as well as of phenolic and aminic antioxidants was published by Hummel and Scholl [21]. UV absorbance data for isolated chromophores are listed elsewhere [22]. A general UV atlas of organic compounds is available [23]. 

Fluorescence is much more widely used for analysis than phosphorescence. Yet, the use of fluorescent detectors is limited to the restricted set of additives with fluorescent properties. Fluorescence detection is highly recommended for food analysis (e.g. vitamins), bioscience applications, and environmental analysis. As to poly-mer/additive analysis fluorescence and phosphorescence analysis of UV absorbers, optical brighteners, phenolic and aromatic amine antioxidants are most recurrent [25] with an extensive listing for 29 UVAs and AOs in an organic solvent medium at r.t. and 77 K by Kirkbright et al. [149]. 

Fluorescence in UV radiation is a frequently used method for detection of TLC spots, e.g. of Tinuvin 326 [42]. The fluorescence emitted by optical brighteners under UV light on a thin-layer plate has been utilised as a means of analysing these compounds [42]. On the whole, the use of fluorescence detection in poly-mer/additive analysis of extracts is certainly not overwhelming. Applied fluorescence has been described in a monograph [156]. 

Descriptive terms such as fluorescent whitening agents , optical brighteners and optical bleaches have all been used for the products described in this chapter as FBAs. Many of these terms have validity and the term fluorescent brightening agents is preferred here only because it has been adopted in the indexes of Chemical Abstracts. 

While many commercial optical brighteners are trade secrets, most of these fluorescent compounds contain one or more ring systems and are derivatives of stilbene (Fig. 12.8.1), coumarin (Fig. 12.8.2), imidazole (Fig. 12.8.3), triazole... 

When part of an extended conjugated system, 2,5-disubstituted-l,3,4-oxadiazoles often fluoresce. This makes them potentially useful as laser dyes, optical brighteners, and scintillators. For example, oxadiazole (121a) <84GEP(O)3245202> and l,4-bis-(5-phenyl-l,3,4-oxadiazol-2-yl)naphthalene... 

Fluorescence Photons (UV, visible or near-IR) Pigments, inks, optical brighteners, safety signs and clothing, analysis, biology, molecular electronics... 

The photophysical phenomena of fluorescence and phosphorescence have found varied applications in fluorescent tube lights, X-ray and TV screens, as luminescent dials for watches, as optical brighteners in white dress materials, as paints in advertisement hoardings which show enhanced brilliance by utilizing fluorescence, for detection of cracks in metal work, for tracing the course of river through caves, as microanalytical reagents, and so on. 

Colourless molecules with blue fluorescence are optical brightening agents that are used as blue whiteners in paper production and washing powders (see Chapter 7). The two main classes are heterocylics such as pyrazolines and particularly stilbenes (1). 

Figure 7.2 illustrates the processes involved in light absorption and fluorescence by optical brighteners [4-8],... 

Figure 7.3 Typical absorption (A) and fluorescence (F) spectra of optical brighteners [25] F i = dilute solution F2 = applied to substrate...

Optical brightening was discovered in 1929 by P. Krais [22], The whiteness of viscose rayon and semibleached flax yam was increased by treatment with an aqueous solution of esculin (1) [531-75-9] and drying. Krais recognized that this effect was due to the strong blue fluorescence of esculin, a 3-D-glucoside of 6,7-dihy-droxycoumarin that is obtained by extracting horse chestnut bark. (For historical references, see [23].)... 

Although the intense blue fluorescence of l,3-diphenyl-2-pyrazolines had long been known [86], the usefulness of these compounds as optical brighteners was not recognized until 1949 [87], The most valuable brighteners are the 3-(4-chloro-phenyl)-l-(4-phenylsulfonic acid) derivatives because of their ready manufacturing ability, excellent optical properties, and versatility in application. 

The 4-aminonaphthalimides and their /V-alkylatcd derivatives are brilliant greenish yellow fluorescent dyes. A cylation of the amino group at the 4-position of the naphthalimide ring shifts the fluorescence toward blue [111], yielding compounds suitable for use as optical brighteners, such as 4-acetylamino-7V-(//-butyl)naph-thalimide [3353-99-9] [112],... 

Optical brighteners (fluorescent whitening agents, FWAs) are used primarily in the textile, detergent, and paper industries and are also added to plastics [118], The mode of application and performance requirements differ greatly from one substrate to another, but there are five common basic principles ... 

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